An example of a known planetary gear structure is disclosed in Japanese Utility Model No. 2508622. This known planetary gear structure is constructed to fit a plurality of pinion shafts within a carrier.
FIGS. 4–7 illustrate an example of a known planetary gear structure 11 which is adapted to be assembled within a transmission. The planetary gear structure 11 includes a single stopper plate 106 which holds six pinion shafts 101 within a carrier 100. Each of the pinion shafts 101 has a slit 103 so as to engage with the stopper plate 106. The stopper plate 106 has three projecting portions 107, each of which is arranged on the outer circumference of the stopper plate 106 so that adjacent projecting portions 107 are spaced apart from one another at equal angular intervals. Each of the projecting portions 107 is engaged with a bore 108 of the carrier 100 as shown in FIG. 6 for fixing the stopper plate 106 against rotation after assembly. Here, the carrier 100 is attached to a housing 12 of the transmission.
To fix the pinion shafts 101 with the carrier 100, each of the pinion shafts 101 is inserted into a respective receiving bore. Then, the stopper plate 106 is rotationally positioned so that the stopper plate 106 is near the predetermined pinion shafts 101. This condition is shown by the broken line position in FIG. 5. Further, the stopper plate 106 is rotated in the counter-clockwise direction so that the slit 103 of each pinion shaft 101 engages or receives a portion of the stopper plate 106. This condition is shown by the solid line position in FIG. 5. At that time, the projecting portions 107 are also engaged with the carrier 100.
A purpose of the pinion shafts 101 is not only to rotatably support the pinions, but also to lubricate the oil-supplying passages 4, 5. The lubricating oil is supplied to a bearing supporting the pinions, engagement portions between the pinion and a sun gear, engagement portions between the pinion and a ring gear, and engagement portions between the pinions. Therefore, the purpose of the stopper plate 106 for holding pinion shafts 101 is not only to fix the pinion shafts 101 to the carrier 100, but also to prevent the pinion shafts from rotating on their respective axes and allow the openings of the oil-supplying passages to be appropriately positioned.
However, with the planetary gear structure 11 shown in FIGS. 4–7, because all of the pinion shafts 101 are fixed to the carrier 100 by way of the single stopper plate 106, it is necessary that the position arrangements of the pinion shafts 101 be simultaneously done. Thus, the assembling time of the pinion shafts 101 is relatively long and the working thereof is somewhat troublesome. Further, because the stopper plate 106 is formed as a single piece, the fabrication of the stopper plate 106 can be relatively complicated.